Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

597
FXUS63 KLOT 161135
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
635 AM CDT Mon Mar 16 2026

.KEY MESSAGES...

- The worst of the winter storm will be from now through about 9
  AM with occasional blizzard conditions across northwestern
  Illinois and periods of snow and low visibility as far east
  as the Lake Michigan shoreline.

- Snow will taper from south to north after daybreak before snow
  showers redevelop this afternoon. Wind chills will remain in
  the single digits to lower teens today.

- Tonight will be unseasonably chilly with overnight wind
  chills ranging from 0 to locally 15 below.

- A clipper system will bring a period of snow to the area
  Tuesday night into Wednesday morning. Thereafter, a warming
  trend will commence through the end of the week.

&&

.UPDATE...
Issued at 635 AM CDT Mon Mar 16 2026

Recent regional radar imagery depict the best banded snow
lifting northeastward toward Lake Michigan. With that said,
broad upper-level diffluence in the right exit region of a
100kt+ 500mb jet nosing into Michigan will maintain a broad
shield of light/low-intensity snow across northern Illinois
through about 9 or 10 AM this morning. When combined with
northwesterly winds gusting >35 mph, travel conditions will
remain slippery to locally hazardous with the worst conditions
west of I-39 and north of I-80.

While we`ve struggled to meet true blizzard criteria, will
maintain the current configuration of headlines for the time
being and let the day shift make adjustments as the back edge of
snow works northward.

Borchardt

&&

.DISCUSSION...
Issued at 241 AM CDT Mon Mar 16 2026

Early morning GOES-19 water vapor imagery depicts the classic
evolution of a maturing synoptic-scale cyclone, with an
expansive warm conveyor belt extending from the Gulf Coast up
into southern Ontario, a dry slot arcing from the Ozarks
northeastward into northern Illinois, and an elongated
deformation zone stretching across the western Great Lakes.
Based on surface observations, the center of the surface low is
currently located over Benton Harbor, Michigan. When looking at
regional pressure traces over the past 24 hours, the path of the
center of the low has been on the very southern end of ensemble
cluster paths with a notable southern trend established in each
successive ensemble mean forecast over the past four successive
runs. As a result, the deformation "comma head" region is
verifying southeast of ensemble guidance, and is largely
centered from the Mississippi River to Interstate 39. An
interesting note this morning is the clear passage of several
mesoscale gravity waves through the deformation shield, which
was well advertised by CAM guidance 24 hours ago. Each wave was
marked by a local increase in snowfall rates and wake
subsidence, as well as locally higher winds (over 60 mph in
southeastern Wisconsin).

We`re heading into the time window of worst conditions.
Snowfall rates are expected to peak in the 1 to 2"/hr range from
now through 4 to 5 AM across northwestern Illinois. When
combined with the continued fall of temperatures as well as an
increase in northwesterly winds gusting 40 to 45 mph, occasional
blizzard conditions (visibility down to 1/4SM) are expected
generally northwest of a line from Mendota to Antioch, lasting
through daybreak or shortly thereafter. Total snowfall between
now and 9 AM should range from 4 to locally 9 inches, though
considerable blowing and drifting snow may make it difficult to
actually verify measurements. Nevertheless, a Blizzard Warning
remains in effect for Lee, Ogle, DeKalb, Winnebago, Boone, and
McHenry County. Non-essential travel should be avoided in this
area.

Meanwhile, east of the Blizzard Warning, precipitation rates
and types at press time are largely a fine freezing mist or
poor- quality snowflakes, which is typical in the dryslot of
synoptic-scale cyclone. With that said, have been earnestly
watching the eastward expansion eastward of a transition back to
snow and a modest increase in snow rates over the past hour,
which should reach Chicago and the Lake Michigan shoreline by 3
AM. Through the overnight hours, a general 1 to 4 inches seems
like a good bet between I-39 and the Lake Michigan shoreline
with the lowest amounts with eastward extent. Even with more
limited snowfall amounts, northwesterly winds gusting 40 to 45
mph will nevertheless reduce visibility leading to locally
hazardous travel conditions (especially in open and rural areas)
by daybreak. Winter Weather Advisories for roughly the I-55
corridor westward remain in effect for this reason. Little to no
snow should fall in northwestern Indiana.

After daybreak, the center of the surface low will lift toward
Lake Huron. As a result, the back edge deformation shield should
lift northward into Wisconsin and Lower Michigan with time
leading to snow rates becoming increasingly light (down to
0.1"/hr) across northern Illinois. Snow should end outright from
south to north generally in the 7 AM to 10 AM window, give or
take an hour. A tight pressure gradient will remain entrenched
across the Great Lakes today even as the low pulls away thanks
to a 1025+mb surface high in the Plains. Accordingly,
northwesterly winds will remain strong today with frequent gusts
of 35 to 45 mph. The forecast high temperatures in the low to
mid 20s will hence feel more like the single digits to lower
teens. Later this afternoon, approaching upper-level shortwaves
embedded in the deep cyclonic flow aloft as well as cooling
mid- level temperatures will support the generation of scattered
snow showers. While this pattern doesn`t quite meet the
conceptual model for snow squalls, can easily envision
visibility dropping below a mile in the most intense snow
showers given the aforementioned gusty northwest winds.

Tonight will be downright chilly! The core of the coldest 850mb
air near minus 20 C will slide overhead during the overnight
hours, which with continued cold air advection will cause
overnight lows to the lower single digits (northwest) to lower
teens (southeast). Wind chills will fall to the 0 to locally
minus 15 range, coldest around Rockford. Bundle up when heading
out the door Monday morning!

Borchardt


Tuesday through Sunday:

The unseasonably cold start to the day on Tuesday will lower
the ceiling for the day`s high temperatures, which are expected
to only climb into the 20s (and possibly not even out of the
upper teens in areas where our newly minted snowpack is at least
a few inches deep). With expansive surface high pressure
shuffling its way eastward across the region, no precipitation
is expected during the daytime hours on Tuesday.

A fast-moving clipper-type shortwave diving southeastward out
of Alberta will arrive at our doorstep early Tuesday evening.
Ensemble and deterministic model guidance is pretty much in
unanimous agreement that an associated swath of snow will spread
over our forecast area shortly thereafter and persist through a
good chunk of the night before departing Wednesday morning. A
notable amount spread remains in the QPF output of the various
global ensemble systems with the GEFS favoring a wetter/snowier
outcome (ensemble mean QPF range of around 0.10-0.20") compared
to the EPS (ensemble mean QPF range of around 0.05-0.10").
Meanwhile, the 00Z CMCE depicts a happy medium between the 00Z
GEFS and EPS, with its ensemble mean QPF settling in at around
0.07-0.13".

Snow-to-liquid ratios during this snowfall will start off
higher-than-average with near-surface air temperatures initially
in the teens/low 20s, but should trend towards a more average
10-12:1 ratio before the snow ends as temperatures gradually
rise overnight. Considering everything altogether, a realistic
higher-end outcome for this event would be a swath of 2-4" snow
accumulations across our CWA if a wetter GEFS-like solution
were to come to fruition. This scenario would also present the
greatest impacts to the Wednesday morning commute. On the other
hand, if a drier EPS-like outcome were to be realized, then
snow accumulations across our CWA would largely end up at or
below 1". Our gridded NBM-based forecast currently depicts a
"middle ground" solution between these outcomes while we wait
to see model guidance converge on an common solution.

A strong upper-level ridge initially centered off the California
coast will reposition itself eastward over the Desert Southwest
for the latter half of the week. This will kick off a warming
trend here locally through the end of the workweek as the
associated thermal ridge expands eastward, with highs in the 50s
and 60s expected to make a return by the end of the week. The
jet stream draped around the ridge`s northern periphery will
also get nudged eastward, which will steer any subsequent
clipper waves/systems emanating out of Canada more to our east.
That said, one additional clipper shortwave may still get close
enough to our area Wednesday night into Thursday for another
round of precipitation to occur here. This outcome continues to
be reflected only in a minority of Grand Ensemble members,
however, and the favored forecast solution at this time is one
that keeps most or all of our forecast area dry during this time
period.

Ogorek

&&

.AVIATION /12Z TAFS THROUGH 18Z TUESDAY/...
Issued at 619 AM CDT Mon Mar 16 2026

A regional winter storm will come to an end through the first 6
to 8 hours of the TAF period. While the general expectation is
for snow intensity to gradually wane through the morning,
strengthening northwesterly winds with gusts >30kt will
nevertheless maintain relatively low visibility with
observations only gradually climbing toward 3SM toward 15Z and
6SM toward 18Z. With cold air advection behind the departing
system leading to diurnal instability, current thinking is that
snow showers will develop by early afternoon leading to
intermittent visibility drops to 2-3SM. Northwesterly wind gusts
to 30 kt and snow showers or flurries may very well continue
all the way through 06Z tonight. Cigs are expected to remain
largely MVFR today before scattering out tonight.

Borchardt

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Blizzard Warning until 1 PM CDT this afternoon for ILZ003-
     ILZ004-ILZ005-ILZ008-ILZ010-ILZ011.

     Winter Weather Advisory until 1 PM CDT this afternoon for
     ILZ006-ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ032-ILZ103-
     ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.

IN...None.
LM...Gale Warning until 10 PM CDT this evening for the IL and IN
     nearshore waters.

&&

$$

Visit us at weather.gov/chicago